1. Technical Field
This application relates to a vascular device and more particularly to a vascular device for approximating vein valve leaflets for treating venous valve insufficiency.
2. Background of Related Art
Veins in the body transport blood to the heart and arteries carry blood away from the heart. The veins have one-way valve structures in the form of leaflets disposed annularly along the inside wall of the vein which open to permit blood flow toward the heart and close to prevent back flow. That is, when blood flows through the vein, the pressure forces the valve leaflets apart as they flex in the direction of blood flow and move towards the inside wall of the vessel, creating an opening therebetween for blood flow. The leaflets, however, do not normally bend in the opposite direction and therefore return to a closed position to prevent blood flow in the opposite, i.e. retrograde, direction after the pressure is relieved. The leaflet structures, when functioning properly, extend radially inwardly toward one another such that the tips contact each other to block backflow of blood.
In the condition of venous valve insufficiency, the valve leaflets do not function properly as they thicken and lose flexibility, resulting in their inability to extend sufficiently radially inwardly to enable their tips to come into sufficient contact with each other to prevent retrograde blood flow. The retrograde blood flow causes the buildup of hydrostatic pressure on the residual valves and the weight of the blood dilates the wall of the vessel. Such retrograde blood flow, commonly referred to as reflux, leads to swelling and varicose veins, causing great discomfort and pain to the patient. Such retrograde blood flow, if left untreated can also cause venous stasis ulcers of the skin and subcutaneous tissue. There are generally two types of venous valve insufficiency: primary and secondary. Primary venous valve insufficiency is typically a condition from birth, where the vein is simply too large in relation to the leaflets so that the leaflets cannot come into adequate contact to prevent backflow. More common is secondary venous valve insufficiency which is caused by clots which gel and scar, thereby changing the configuration of the leaflets, i.e. thickening the leaflets creating a xe2x80x9cstub-likexe2x80x9d configuration. Venous valve insufficiency can occur in the superficial venous system, such as the saphenous veins in the leg, or in the deep venous system, such as the femoral and popliteal veins extending along the back of the knee to the groin.
A common method of treatment of venous valve insufficiency is placement of an elastic stocking around the patient""s leg to apply external pressure to the vein, forcing the walls radially inwardly to force the leaflets into apposition. Although sometimes successful, the tight stocking is quite uncomfortable, especially in warm weather, as the stocking must be constantly worn to keep the leaflets in apposition. The elastic stocking also affects the patient""s physical appearance, thereby potentially having an adverse psychological affect. This physical and/or psychological discomfort sometimes results in the patient remove the stocking, thereby preventing adequate treatment.
Another method of treatment has been developed to avoid the discomfort of the stocking. This method involves major surgery requiring the implantation of a cuff internally of the body, directly around the vein. This surgery requires a large incision, resulting in a long patient recovery time, scarring and carries the risks, e.g. anesthesia, inherent with surgery.
Another invasive method of surgery involves selective repairing of the valve leaflets, referred to as valvuloplasty. In one method, sutures are utilized to bring the free edges of the valve cusp into contact. This procedure is complicated and has the same disadvantages of the major surgery described above.
It would therefore be advantageous to provide a method and device to minimally invasively treat venous valve insufficiency without requiring an outer stocking or internal cuff. Such device would thereby avoid the physical and psychological discomfort of an external stocking as well as avoid the risk, complexity and expense of surgically implanted cuffs. Such device would advantageously be inserted minimally invasively, i.e. intravascularly, and function to effectively bring the valve leaflets into apposition.
The present invention overcomes the problems and deficiencies of the prior art by providing an intravascular device which brings the vessel wall adjacent the vein valve radially inwardly to bring valve leaflets into apposition. The present invention, in one aspect, provides a vascular device movable from a collapsed insertion position having a first diameter to an expanded position having a second larger diameter. A plurality of vessel engaging members extend outwardly from the device for securely engaging the internal wall of a vessel upon expansion of the device to the second expanded position. The vessel engaging members pull the internal wall of the vessel radially inwardly upon movement of the device from the second expanded position toward a first expanded position having a third diameter greater than the first diameter and smaller than the second diameter.
The device is preferably composed of shape memory material and the first expanded position preferably substantially corresponds to the memorized position of the device. In one embodiment, the device is initially movable from the collapsed position to the first expanded position in response to exposure to body temperature and is subsequently movable to the second expanded position by mechanical means or an inflatable balloon positioned within the device. In another embodiment, the device is movable from the collapsed position to the second expanded position by substantial simultaneous exposure to body temperature and expansion by an expandable member.
The vessel engaging members preferably extend from the distal and proximal portions of the device and have sharp ends to limit axial movement of the vessel wall and barbs to limit radial movement of the vessel wall to enhance retention (securement) of the vessel. The vessel engaging members preferably extend substantially parallel to a longitudinal axis of the device in the collapsed position and substantially perpendicular to the longitudinal axis in the extended position.
In one embodiment, in the collapsed position the middle portion of the device includes a plurality of longitudinal strips with a gap between adjacent strips. In this embodiment, the vessel engaging member is formed by a cut in the respective longitudinal strip and the longitudinal strips buckle radially outwardly upon movement of the device to the first expanded position.
In another embodiment of the present invention, the device includes a plurality of longitudinal strips, each terminating at opposing ends in one of the vessel engaging members. A substantially straight slot can be formed in each of the longitudinal strips in the collapsed position of the device, each slot preferably transforming to a substantially diamond shape when the device is moved to the first expanded position.
In another aspect of the present invention, a vascular device is provided comprising a tubular-like member expandable from a collapsed configuration to an expanded configuration and having a plurality of hooks extending from the tubular member at the proximal end and the distal end. The hooks extend substantially parallel to the longitudinal axis in the collapsed position and substantially perpendicular to the longitudinal axis in the extended position. Barbs may be provided adjacent the hooks for limiting radial movement of a vessel wall engaged by the barbs.
In another aspect of the present invention, a vascular device is provided comprising a tubular-like member expandable from a collapsed configuration to an expanded configuration. A plurality of vessel engaging members with penetrating tips extend from the proximal, distal and intermediate portions. Expansion of the member to the expanded configuration causes the distal and proximal portions to move axially inwardly and the intermediate portion to buckle radially outwardly to enable the vessel engaging members to securely engage the vessel wall.
In another aspect of the present invention, an expandable vascular device is provided comprising a framework movable from a collapsed configuration for delivery to a target vessel to an expanded configuration for retaining the vessel. The framework is formed by a plurality of longitudinal strips with adjacent longitudinal strips formed by connecting ribs, and each of the longitudinal strips terminating at opposing ends in a vessel wall penetrating member to engage the vessel wall. In this embodiment, a longitudinal slot is preferably formed in each of the longitudinal strips such that the longitudinal slot forms a substantially diamond shaped slot in the expanded configuration of the device. The longitudinal slots are preferably in substantial axial alignment. The connecting ribs can also be in substantial axial alignment.
The present invention also provides a vascular system comprising a balloon catheter having an elongated shaft and an expandable balloon and a vascular device mounted over the expandable balloon and composed of shape memory material and having a collapsed position and a memorized position. The vascular device is expandable to an expanded position to engage the vessel walls and returnable substantially to the memorized position to bring the walls radially inwardly.
In one embodiment the vascular device is expandable first to the memorized condition in response to exposure to body temperature and subsequently expanded to the expanded position by inflation of the balloon. In another embodiment, the vascular device is expandable to the expanded position as the device is substantially simultaneously exposed to body temperature and the balloon is inflated. The vascular device can be connected to the balloon. A pair of looped sutures can be provided to connect the vascular device to the balloon, the sutures separable from the vascular device upon expansion of the balloon to a predetermined size.
The present invention also provides a method for treating venous valve insufficiency comprising:
inserting a delivery device and a vascular device into a target vessel adjacent valve leaflets of the vessel;
deploying the vascular device to an enlarged diameter to securely engage an internal wall of the vessel; and
reducing the diameter of the vascular device to move the vessel wall radially inwardly and bring the valve leaflets closer together.
In one embodiment, the method further includes the step of deploying the vascular device to a first expanded diameter prior to deploying the vascular device to the enlarged diameter, wherein the first expanded diameter is less than the enlarged diameter. The step of deploying the vascular device to the enlarged diameter can include the step of inflating a balloon positioned within the device. The step of deploying the vascular device to the first expanded diameter preferably comprises the step of exposing the vascular device from a delivery sheath to enable the vascular device to return to a shape memorized configuration in response to being warmed by body temperature. In another embodiment, the step of deploying the vascular device to an enlarged diameter comprises releasing the vascular device from the delivery device to enable it to return to a shape memorized condition and substantially simultaneously inflating a balloon.
The step of deploying the vascular device to an enlarged diameter can move a plurality of penetrating tips of vessel engaging members of the vascular device to a position substantially perpendicular at another angle to a longitudinal axis of the vascular device to engage the internal wall of the vessel.
The present invention also provides a method of approximating vein valve leaflets comprising:
inserting a vascular device of shape memory material in a collapsed configuration intravascularly to a target vessel;
actuating an expandable member to expand the vascular device to a further expanded configuration to enable wall engaging members of the device to retain the internal vessel wall; and
contracting the expandable member to allow the vascular device to contract towards it memorized expanded configuration to bring the valve leaflets closer together.
In one embodiment, the method further comprises the step of releasing the vascular device from a delivery sheath to enable it to return to its memorized expanded configuration prior to the step of actuating the expandable member. In another embodiment, the device returns to the memorized expanded configuration in response to exposure to body temperature and the step of actuating the expandable member to expand the vascular device occurs substantially simultaneously with exposure of the device to body temperature.
The wall engaging members preferably each have penetrating tips and the step of actuating the expandable member causes the penetrating tips disposed on a proximal portion and a distal portion of the vascular device to secure the internal vessel wall.
In the foregoing methods the delivery device can be inserted to a position upstream (with respect to blood flow) of the valve leaflets to deliver the vascular device upstream of the valve leaflets. Alternatively it can be inserted to a position downstream of the valve leaflets to deliver the vascular device downstream of the valve leaflets. The delivery device can be inserted through the jugular vein or femoral vein into the popliteal vein or the saphenous vein, or directly into these veins.